Sensitive and quantitative in vivo analysis of PD-L1 using magnetic particle imaging and imaging-guided immunotherapy
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Magnetic Particle Imaging
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The optimization of magnetic nanoparticles (MNPs) as markers for magnetic particle imaging (MPI) requires an understanding of the relationship between the harmonics spectrum and the structural and magnetic properties of the MNPs. Although magnetic particle spectroscopy (MPS) - carried out at the same excitation frequency as the given MPI system - represents a straightforward technique to study MNPs for their suitability for MPI, a complete understanding of the mechanisms and differences between different tracer materials requires additional measurements of the static and dynamic magnetic behavior covering additional field and time ranges. Furthermore, theoretical models are needed, which correctly account for the static and dynamic magnetic properties of the markers. In this paper, we give an overview of currently used theoretical models for the explanation of amplitude and phase of the harmonics spectra as well as of the various static and dynamic magnetic techniques, which are applied for the comprehensive characterization of MNPs for MPI. We demonstrate on two multicore MNP model systems, Resovist(®) and FeraSpin™ Series, how a detailed picture of the MPI performance can be obtained by combining various static and dynamic magnetic measurements.
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Abstract Magnetic particle imaging (MPI) is a young imaging modality for biomedical applications. It uses magnetic nanoparticles as a tracer material to produce three-dimensional images of the spatial tracer distribution in the field-of-view. Since the tracer magnetization dynamics are tied to the hydrodynamic mobility via the Brownian relaxation mechanism, MPI is also capable of mapping the local environment during the imaging process. Since the influence of viscosity or temperature on the harmonic spectrum is very complicated, we used magnetic particle spectroscopy (MPS) as an integral measurement technique to investigate the relationships. We studied MPS spectra as function of both viscosity and temperature on model particle systems. With multispectral MPS, we also developed an empirical tool for treating more complex scenarios via a calibration approach. We demonstrate that MPS/MPI are powerful methods for studying particle-matrix interactions in complex media.
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Background: Combining magnetic particle imaging (MPI) and magnetic fluid hyperthermia (MFH) offers the ability to perform localized hyperthermia and magnetic particle imaging-assisted ther-mometry of hyperthermia treatment. This allows precise regional selective heating inside the body without invasive interventions. In current MPI-MFH platforms, separate systems are used, which require object transfer from one system to another. Here, we present the design, development and evaluation process for integrable MFH platforms, which extends a commercial MPI scanner with the functionality of MFH. Methods: The biggest issue of integrating magnetic fluid hyperthermia platforms into a magnetic par-ticle imaging system is the magnetic coupling of the devices, which induces high voltage in the imaging system, and is harming its components. In this paper we use a self-compensation approach derived from heuristic algorithms to protect the magnetic particle imaging scanner. The integrable platforms are evaluated regarding electrical and magnetic characteristics, cooling capability, field strength, the magnetic coupling to a replica of the magnetic particle imaging system's main solenoid and particle heating. Results: The MFH platforms generate suitable magnetic fields for magnetic heating of particles and are compatible with a commercial magnetic particle imaging scanner. In combination with the imaging system, selective heating with a gradient field and steerable heating positioning using the MPI focus fields are possible. Conclusion: The proposed MFH platforms serve as a therapeutic tool to unlock MFH functionality of a commercial magnetic particle imaging scanner, enabling its use in future preclinical trials of MPI-guided, spatially selective magnetic hyperthermia therapy.
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Magnetic Particle Imaging (MPI) is a promising tomographic modality using magnetic nanoparticles (MNP) as probes for diagnostic purposes in biomedicine. The MPI signal quality crucially depends on the magnetic properties of the MNP as well as on the influence of the surrounding biological environment. Therefore, different physiological parameters like pH-value, salt concentration, mobility may have distinct impact on the MPI signal performance. We used Magnetic Particle Spectroscopy, the zero-dimensional MPI, to monitor the potential MPI performance of Resovist and Feraheme MNP in different physiological media as a function of time.
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Magnetic Particle Imaging
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The ferrohydrodynamic properties of magnetic nanoparticles govern resolution and signal strength in magnetic particle imaging (MPI), a medical imaging modality with applications in small animals and humans. Here, we discuss the development and key results of a magnetic particle relaxometer that measures the core diameter and relaxation constant of magnetic nanoparticles. This instrument enables us to directly measure the one-dimensional MPI point spread function. To elucidate our results, we develop a simplified ferrohydrodynamic model that assumes nanoparticles respond to time varying magnetic fields according to a Debeye model of Brownian relaxation, which we verify with experimental data.
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Magnetic Particle Imaging (MPI) is a novel imaging modality that uses various static and oscillating magnetic fields to image the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIONs) with high sensitivity and no ionizing radiation. A Magnetic Particle Spectrometer (MPS) is used to measure the characteristics of SPIONs and achieve the system matrix of the imaging devices. A three-dimensional MPS has been presented lately including its first measurement results. In this paper, a temperature control setup in the MPS is introduced and its feasibility of controlling the sample temperature is demonstrated.
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Magnetic nanoparticles (MNPs) have been widely studied for biomedical applications such as separation of biological targets, immunoassays, drug delivery, hyperthermia, and magnetic particle imaging (MPI). In particular, MPI is a new modality for imaging the spatial distribution of the MNPs, especially for in-vivo diagnostics.
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Background: Combining magnetic particle imaging (MPI) and magnetic fluid hyperthermia (MFH) offers the ability to perform localized hyperthermia and magnetic particle imaging-assisted thermometry of hyperthermia treatment.This allows precise regional selective heating inside the body without invasive interventions.In current MPI-MFH platforms, separate systems are used, which require object transfer from one system to another.Here, we present the design, development and evaluation process for integrable MFH platforms, which extends a commercial MPI scanner with the functionality of MFH.Methods: The biggest issue of integrating magnetic fluid hyperthermia platforms into a magnetic particle imaging system is the magnetic coupling of the devices, which induces high voltage in the imaging system, and is harming its components.In this paper, we use a self-compensation approach derived from heuristic algorithms to protect the magnetic particle imaging scanner.The integrable platforms are evaluated regarding electrical and magnetic characteristics, cooling capability, field strength, the magnetic coupling to a replica of the magnetic particle imaging system's main solenoid and particle heating.Results: The MFH platforms generate suitable magnetic fields for the magnetic heating of particles and are compatible with a commercial magnetic particle imaging scanner.In combination with the imaging system, selective heating with a gradient field and steerable heating positioning using the MPI focus fields are possible. Conclusion:The proposed MFH platforms serve as a therapeutic tool to unlock the MFH functionality of a commercial magnetic particle imaging scanner, enabling its use in future preclinical trials of MPI-guided, spatially selective magnetic hyperthermia therapy.
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